The concept of utilizing lime for carbon dioxide capture has existed for well over a century. It was first introduced by DuMotay and Marechal in 1869 for enhancing the gasification of coal using lime followed by CONSOL's CO2 acceptor process a century later when this concept was tested in a 40 tons/day plant. A variation of this process called the Hypring process was developed in Japan for the production of hydrogen at high pressures. Harrison et al. and Grace et al. have also applied this concept to the production of hydrogen both from Syngas by the water gas shift reaction and methane by the sorption enhanced steam methane reforming reaction. Silaban et al. studied the reversibility of the carbonation reaction for the production of hydrogen.
Within the last decade research has also focused on the use of lime for carbon dioxide capture from combustion flue gas. Shimizu et al. conceptually designed a process that uses twin-fluidized bed reactors for capturing carbon dioxide from a coal combustion power plant. After the conceptual design, a significant amount of research has advanced the concept greatly. The contribution of John R. Grace from the University of British Columbia, Juan Carlos Abanades from Instituto Nacional del Carbon-CSIC and CANMET energy Technology Centre have further enhanced the understanding of the Chemical Looping Technology using lime sorbent for the capture of CO2. In addition, the reversibility of the carbonation reaction, the investigation of the decay of CO2 capture over multiple cycles of carbonation and calcination and the production layer formation have been studied by Barker et al., Bhatia and Perlmutter and Mess et al. respectively.
The regenerability of the calcium oxide sorbent has been the major draw back of high temperature calcium based CO2 capture processes. CaO oxide sorbents are prone to sintering during to the regeneration step which is conducted at high temperatures. Over multiple cycles sintering progressively increases and reduces the CO2 capture capacity of the sorbent. Sintering results in an increase in solid circulation and make up rate. Research has been conducted to develop methods of reducing the sintering of the sorbent. Pretreatment methods have been developed at the CANMET Energy Center which involves hydration of the calcined sorbent at 100° C. at atmospheric pressure and saturation pressure, powdering the sorbent and preheating the sorbent in a nitrogen atmosphere. The sintering of the sorbent was reduced when these pretreatment methods were applied to the sorbent. This concept developed by CANMET Energy Center is only a pretreatment method and is applied to the sorbent once in 20 cycles and sorbent sintering still occurs resulting in a reduction in CO2 capture capacity. This concept has been tested by Manovic et al. in TGA, fixed bed and a 75 KWth dual fluidized bed combustion plant.
Grace et al. have also investigated the pretreatment of the sorbent by hydration at atmospheric pressure at 150° C. and 300° C. From thermodynamics it is seen that complete hydration does not occur spontaneously at temperature of 300° C. and hence complete reactivation of the sorbent is not achieved by these methods. In addition, this method has also been developed to be applied once in a few cycles and hence sorbent degradation still occurs.
The reactivation of the sorbent by recarbonation has also been investigated but this process requires an additional calcination step which is very energy consuming and uneconomical.
Zeeman et al. have integrated the hydration process as a reactivation step in the CO2 removal process. They hydrate the sorbent at 300° C. in the presence of CO2 and steam at atmospheric pressure. There has been no mention about the extent of hydration achieved by this process and the amount of carbonation occurring during the hydration process. Although this method was found to reduce sintering and reactivate the sorbent a steady decline in the reactivity of the sorbent was still observed.
Consequently, it can be understood that there is a need for a cost effective and efficient system and method to minimize the sintering of the selected sorbent and overcome the sorbents decay in reactivity. Exemplary systems and methods of the inventive concept satisfy these needs/preferences.